U.S. Pat. No. 5,000,129 to Fukada et al., issued Mar. 19, 1991, for "Intake System For Internal Combustion Engine" discloses an air intake system for a V-block engine having a central surge tank disposed above the space between the left and right cylinder banks of the engine. This surge tank is operatively integrated with left and right side surge tanks extending above respective banks of cylinders. A communicating passage disposed between discrete side intake passages connects the central surge tank with the left and right surge tanks so that all of the tanks combine to serve as a single surge tank having a large volume for the suppression of intake air interference.
U.S. Pat. No. 5,133,308, issued Jul. 28, 1992, to Hitomi et al., for "Intake System For Engine" discloses an intake system for a V-block internal combustion engine having a centralized junction chamber and a plurality of discrete intake passages connecting the junction chamber with respective cylinders of the engine. Rotary valves in the intake passages are operated by actuators responding to a controller that receives engine speed signals to close and open the valves for improving engine torque.
U.S. Pat. No. 5,590,629, issued Jan. 7, 1997, to Patyi et al., for "Multi-mode Intake Manifold Assembly for Internal Combustion Engines" discloses a three plenum air distribution manifold for directing intake air into an internal combustion engine with long, narrow runners leading from first and second spaced side plenums for delivery of air and recirculating exhaust gases into corresponding combustion chambers for the engine. A third plenum is positioned intermediate the two side plenums to communicate directly with the combustion chambers, bypassing the side plenums. In this manner, intake air is supplied directly to the combustion chambers through short runners which are selectively opened by valves to optimize engine torque over a higher range of engine speeds. In contrast to the relatively complex structures and operation found in U.S. Pat. Nos. 5,000,129 and 5,133,308 and many prior constructions, U.S. Pat. No. 5,133,308 attempts to provide a straight forward three plenum active air distribution manifold for an internal combustion engine operative to generate improved engine torque over the entire range of engine speeds while simultaneously reducing induction noise and variances in pitch.
Although U.S. Pat. No. 5,133,308 does simplify some of the operating structures of U.S. Pat. Nos. 5,000,129 and 5,133,308, a typical construction typically includes a manifold formed of plastic in which the short runner valves are typically formed of metal. In operation, a differential pressure forms across the short runner valves, causing the short runner valve shaft to oscillate. Oscillation of the shaft within the manifold typically produces an audible echo through the plastic manifold. The echo produced by the oscillation of the short runner valve shaft increases the operating noise of the engine and may be heard by those occupying the passenger compartment of the vehicle. The present invention provides a short runner valve shaft biasing assembly which greatly reduces oscillation of the short runner valve shaft and correspondingly reduces chatter of the short runner valves through the plastic manifold and engine compartment.
As stated above, the manifolds described in U.S. Pat. No. 5,133,308 typically are formed of a plastic material. However, the short runner valves and the short runner valve shaft carrying the short runner valves are typically formed of a metal, such as steel or aluminum. The plastic of the manifold and the metal of the short runner valve assembly typically have significantly differing expansion characteristics in response to changes in temperature and humidity. The short runner valve shaft is assembled into the air distribution manifold to enable a predetermined amount of axial movement or endplay of the shaft with respect to the air distribution manifold. Typically, the endplay is controlled at an end of the air distribution manifold opposite the short runner valve shaft control apparatus. In response to expansion or contraction induced by changes in the heat or humidity, the metal and plastic components expand or contract by varying amounts. Because the endplay control is installed at one end of the shaft, the differing expansion of the metal valve shaft assembly and plastic of the air distribution manifold could cause an interference condition between the short runners and the plates which define the short runner valves. This interference condition could cause binding of the shaft, thereby inhibiting operation of the short runner valves. Thus, in contrast to U.S. Pat. No. 5,133,308, the present invention also provides a short runner valve shaft having multiple endplay controls arranged in intermediate positions along the short runner valve shaft, rather than at the end of the valve shaft.